Paw tries to generate the code at best, and doesn't handle all edge cases. Sadly, files/image sending isn't implemented in the code generation for JavaScript... but here's a way to send a file content:
var fileContent = null; // file content comes here
// My API (PUT http://198.11.232.156/oslc/so/triWorkTaskRS/127368846/spi:cstImageIM)
jQuery.ajax({
    url: "http://198.11.232.156/oslc/so/triWorkTaskRS/127368846/spi:cstImageIM",
    type: "PUT",
    headers: {
        "Cookie": "JSESSIONID=...",
        "Authorization": "Basic ...",
        "Content-Type": "image/jpeg",
    },
    processData: false,
    data: fileContent,
})
.done(function(data, textStatus, jqXHR) {
    console.log("HTTP Request Succeeded: " + jqXHR.status);
    console.log(data);
})
.fail(function(jqXHR, textStatus, errorThrown) {
    console.log("HTTP Request Failed");
})
.always(function() {
    /* ... */
});
Now to retrieve a file's content in a web browser, you probably want to use the HTML5 FileReader. Here's an interesting answer for it: https://stackoverflow.com/a/29176118/1698645